If you want to test whether the change in R2 is statistically significant for nested linear models with heteroscedasticity-consistent (HC) standard errors (e.g., hierarchical regression), then you can use vcovHC() from the sandwich package and waldtest() from the lmtest package.

Once you have installed and loaded the sandwich and lmtest packages, you can use the following command to compare two linear models with HC standard errors and return an ANOVA:

waldtest(model1, model2, vcov = function(x) {vcovHC(x, type = "HC3")})

Your options for the estimation type (type) are: type = c("HC3", "const", "HC", "HC0", "HC1", "HC2", "HC4", "HC4m", "HC5"). "HC3" is the default and "const" is used for the unadjusted standard errors directly from the lm objects.

If you have any issues with using waldtest(), particularly if you’re running it in a function, then you will need to fit the linear models using the do.call() function:

# Fits model1
model1 = do.call("lm", list(formula = y ~ x,
                            data = yourData))

# Fits model2 by adding 'z' term to model1
model2 = do.call("update", list(object = model2,
                                formula = "~ . + z"))

# Alternatively, you can enter the full formula for model2
model2 = do.call("lm", list(formula = y ~ x + z,
                            data = yourData))

The above code should look familiar because I used it in the PROCESS Model 1 function described in the previous post.

Category:
Regression, Robust Regression
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